Meconium, a term referring collectively to mucus, bile, epithelial cells, and other products, accumulates in the fetal colon. Meconium is normally excreted within one or two days after birth, however, stress during pregnancy can cause the fetus to expel meconium into the surrounding amniotic fluid. The presence of meconium in the amniotic fluid, "Meconium State Pregnancy," is indicative of a need for more intensive early labor monitoring.
Infants born with meconium in their amniotic fluid have lower overall infant assessment scores than their peers born without meconium in the amniotic fluid. Another danger associated with the presence of meconium is the risk of the infant aspirating meconium into its lungs at the time of birth. Meconium Aspiration Syndrome is a very severe form of pneumonia that is a life-threatening problem for approximately ten to twenty infants per ten thousand born. Meconium Aspiration Syndrome is also a significant cause of cerebral palsy. Because of these and other risks correlated with Meconium State Pregnancy, infants born with meconium in the amniotic fluid (meconium staining) have higher mortality and morbidity rates than infants without meconium staining. A method permitting early prenatal detection of meconium excretion by the fetus would be highly desirable.
Currently, the presence of meconium in the amniotic fluid can be diagnosed only by visualization of dark staining pigments in the amniotic fluid. Meconium staining may be directly visualized by inspection of amniotic fluid at the time of placental membrane rupture, but such late detection is generally not of any practical value. Meconium may be visually detected in amniotic fluid obtained during amniocentesis. This invasive procedure is not performed for all pregnancies, and is too severe a procedure to be considered for routine, e.g. monthly, monitoring of meconium. In addition, amniotic fluid which looks relatively clear by visual inspection may contain significant amounts of meconium.
Recently, a probe has been described which utilizes illumination of the amnion with light of a specific wavelength. The probe detects fluorescence of biological pigments contained within meconium (U.S. Pat. No. 5,172,693). While this procedure permits prenatal detection of meconium, a more specific procedure which does not rely on visual inspection and which may detect smaller amounts of meconium as well as non-colored meconium would be highly desirable.